<template>
  <div>
    <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      // console.log(document.documentElement.scrollTop)
      if (top > 32) {
        let opacity = top / 64
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {
          opacity
        }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .header-abs
    position absolute
    left .4rem
    top .4rem
    width: 2rem
    height: 2rem
    line-height: 2rem
    border-radius: 1rem
    text-align: center
    background: rgba(255, 255, 255, 0.7)
    .header-abs-back
      color: #fff
      font-size: 1.2rem
  .header-fixed
      z-index: 2
      position: fixed
      top: 0
      left: 0
      right: 0
      height: $headerHeight
      line-height: $headerHeight
      text-align: center
      color: #fff
      background: $bgColor
      font-size: .32rem
      .header-fixed-back
        position: absolute
        top: 0
        left: 0
        width: 2rem
        height: 2rem
        text-align: center
        color: #fff
        font-size: 1.2rem
</style>
